Changing site types - also for your opponent?

[Khamul the Easterling]

If by the play of resource events the site type changes, does this apply to versions of your opponent, too?

Examples:
1) Rebuild the town

Playable during the site phase on a non‐Dragonʹs lair, non‐Under‐deeps Ruins&Lairs .The site becomes a Border‐hold and loses all automatic‐attacks.Discard Rebuild the Town when the site is discarded or returned to its location deck

a) If I play RtT on my Hero Weathertop, will my Hero opponent's Weathertop also be regarded ?
b) Will my other aligned opponent's Weathertop also be regarded ?

[CDavis7M]

Sometimes and sometimes not. The text of the card will indicate how the card works.

Rebuild the Town is played on a specific site card and "the site" (that rebuild the town is played on) becomes a border-hold. Your opponent's copy of the site is not "the site" that Rebuild the Town is played on, so the effect does not apply to your opponent's site.

Other cards do affect your opponent's sites. Look at Guarded Haven:

Playable on one of your Wizardhavens [W] other than Isengard, The White Towers, or Rhosgobel. The site is protected. Cards that give Marshaling points are not playable at the site by your opponent in all cases. A company moving to or from this site is not considered moving through the region containing the site (including one less of its region type in their site path).

It is played on your site. The site that it is played on is protected. But not your opponent's site. A company moving to/from that site (that Guarded Haven is played on) is not considered to be moving through the region (pre-errata). But not for your opponent. But the effect "Cards that give Marshaling points are not playable at the site by your opponent in all cases" references the opponent playing cards, which happens at their copy of the site. That effect applies to your opponent.

News of the Shire is not played on a specific site. It is simply played in the play area. The effect "The Shire becomes a border-land, and Bag End becomes a border-hold" is not specific to some particular site because the resource is not played on a site.

This is covered in the CRF under the term "Site": "A permanent-event played on a site affects only the copy of the site it is played on, unless otherwise specified. A permanent-event not played on a site affects all versions of affected sites."

[Khamul the Easterling]

Great, thank you so much for the detailed response!